Powell said the spending is unsustainable. No government other than Trump has so far reduced spending, even Reagan never cut spending he just spent Americas pension system replacing it with IOU's.
So is there room to ponder whether its extenuating circumstances?
After looking at it it seems as though tether has treasuries to back all its tether coins, which means its essentially lending out its coin backed by short term treasuries with 0% interest. So in a way its turning treasuries into a liquid form of money, like cash.
They do buy a small amount of Bitcoin with the profits, which doesn't seem nefarious, MicroStrategy does the similar with its bonds. Its no more nefarious than mortgage backed securities, which let's a buyer inflate the money supply by taking a low interest loan, which is approved by the Fed in order to increase aggregate demand to push a 2% inflation target.